For a variety of reasons debris can accumulate in a wellbore and needs to be removed. This can happen when something is milled out or simply from scale and other foreign material that is normally found on the interior wall of casing.
There are various designs including some that are mounted to a tubular string and employ scrapers for dislodging the debris when the string moves in one direction and a flow diverter into a chamber where the debris is left behind and the fluid continues on a path that eventually bypasses the diverter so that the string is allowed to move up. One example of this design is U.S. Pat. No. 7,562,703. Other examples of debris catchers that rely on string movement are U.S. Pat. No. 7,040,395. Other designs use an eductor to induce circulation which sucks debris into an inlet tube that is centrally located in a housing. The velocity is allowed to slow to let the debris drop into a collection chamber and the flow continues up the housing through a screen and into the eductor inlet for recirculation. Some examples of this design are U.S. Pat. No. 6,276,452 and US Publication 2009/0200010.
A few other examples of debris catchers are in U.S. Pat. Nos. 7,497,260; 7,472,745; 6,227,291 and 6,607,031. There are issues with some of the past designs. The type of catchers that depend on flow diversion with cup seal sometimes use check valves that are in the debris path that can clog or the screens can plug and result in pulling a wet string or triggering a bypass to open so that no debris can be collected. In the circulating type of debris catchers the flow had to go through one or a series of inlet tubes that ultimately led to a single screen near the exit. The debris was supposed to have mostly dropped out before the screen was reached but if the debris was particularly fine it could be carried with the circulation flow to the screen that could clog and all circulation through the tool would stop.
The present invention addresses this issue in a debris catcher that can be in modular form to increase capacity. Each module has an inlet tube that emerges in a preferably cylindrically shaped screen. The debris that enters with a fluid stream has to negotiate two hairpin turns inside a screened space before any debris can either exit or go to the next module. In the negotiation of such turns the debris can drop out. The fluid flow can get through a module by using the cylindrical portion of the screen or the top of the screen since there is a clearance volume around the cylindrical portion of the screen. The top of the screen has an open exit so that the flow with any still entrained debris can exit to the next module or out of the housing, depending on the application. Those skilled in the art will more readily appreciate the present invention from a review of the detailed description of the preferred embodiment and the associated drawing while appreciating that the full scope of the invention is determined by the appended claims.